There is a need in buildings that are susceptible to flooding for valves and vents that allow gas, such as air, to freely pass through in normal conditions but that prevent liquids, such as water, to pass through in flood conditions or in other similar conditions. For example, in buildings that are positioned in flood plains it is desirable to have air bricks to allow free ventilation of the building but it is also desirable that those air bricks do not allow water to enter the building in a flood situation. There have been several proposed solutions to this problem.
One proposed solution is to fit a flood-proof barrier to an outer side of an air brick when flood conditions are anticipated. For example, sand bags, periscopic attachments, or simple seals can be affixed to an air brick before flood conditions occur. However, such solutions are time and labour intensive and require prior knowledge of imminent flooding. Further, it is always necessary to physically remove such barriers after the flooding has abated. In light of these issues valves and vents that automatically prevent the ingress of fluids without the need for input from a user are preferred.
GB2397592 discloses a vent that comprises a float controlled valve having a float positioned within an air flow channel. The float may be a floating ball or cylinder. In a flood situation the float rises on the flood water to seal the air flow channel and prevent water ingress. The device of GB2397592 is relatively complex and expensive to manufacture. In particular, it is difficult to form and mount the float appropriately to provide a waterproof seal in the event of a flood. Therefore, there is a need for a less complex solution.
WO2010/060705 discloses a vent for an air brick comprising an air flow channel and a buoyant flap for sealing the channel in the event of a flood situation. In particular, the flap will normally rest in an open position wherein air can flow through the air flow channel. In a flood situation the flap will be buoyant on the water and rise from an open position to a closed position wherein the air flow channel is sealed. The flap is made buoyant by means of a float member provided on an outer side of the flap. Generally, the float member is provided at or near an upper edge of the flap.
The vent of WO2010/060705 is disadvantageous in that the flap will not be fully closed until the water level has reached the upper edge of the flap in the closed position. As a result, in situations where the water level is above the lower edge of the flap but below the upper edge of the flap in the closed position water may be allowed through the vent, for example by splashing over the top of the flap if the flood water is turbulent.
In light of the above, there is a need for an improved flood prevention device for vents or air bricks that has a simple construction and that will also prevent fluid ingress in all situations.